I. Field of the Invention
The present invention relates to an automotive framing system for accurately positioning upper and lower body components relative to each other prior to securing the body components together.
II. Description of the Prior Art
In the manufacture of automotive vehicles, a conveyor system typically transports a body preassembly sequentially along the conveyor line. Such body preassemblies comprise a lower body component, e.g. the lower body frame, and two or more upper body components which are supported by the lower body component. The upper and lower body components, however, are not fixedly secured to each other in the preassembly. Instead, the upper and lower body components are merely loosely fastened together.
In order to fixedly secure the upper and lower body components together, it is imperative that the upper and lower body components be precisely positioned relative to each other prior to welding or otherwise securing the body components together. In order to accomplish such precision positioning of the upper and lower body components, there have been previously known framing systems.
Two such previously known framing systems are disclosed in U.S. Pat. No. 4,670,961 to Fontaine et al. which issued on Jun. 9, 1987 and U.S. Pat. No. 4,256,947 to De Candia which issued on Mar. 17, 1981. In this prior art framing system, a gantry is positioned above an assembly station at a mid-point of the conveyor line. The gantry includes clamping arms movable between raised and a lowered position. In their raised position, the clamping arms are positioned away from the preassembly to allow the next preassembly to be moved by the conveyor system into the assembly station. Conversely, in their engaged position, the arms swing downwardly while clamps on the anus engage predetermined location points on the various body components and clamp the body components together at a preset position relative to each other. With the body components clamped together, robotic welders or the like are used to fixedly secure the body components together.
In automotive manufacturing operations, however, it is commonplace to utilize the same conveyor line to transport vehicle preassemblies of different body styles. The location points on the body components for these different styles differ from one style to the next.
In order to accommodate different types of vehicles on a common conveyor line, the previously known framing systems have utilized a turntable positioned above the work station and rotatable about a vertical axis. The turntable then indexes to provide up to four different sets of arms and clamps to selectively engage the location points on up to four different styles of automotive vehicles.
The previously known framing systems, however, suffer from a number of disadvantages. One such disadvantage is that, since the framing system is mounted wholly above the assembly station and includes an indexable turntable for bringing different clamping arms into position above the work station, the entire framing system necessarily requires a great amount of headroom at the assembly station. Such headroom, however, may not be available at the automotive manufacturing site. Furthermore, since the entire framing system is elevated above the assembly station, maintenance and maintenance access is rendered more difficult.
A still further disadvantage of these previously known framing systems is that the clamping arms are repeatedly moved between their raised and their lowered position. Such movement of the arms necessarily results in wear after prolonged activation. Such wear, together with the tolerances required to permit the movement of the arms between the raised and lowered position as well as rotation of the turntable translates into increased tolerances between the clamps on the framing system and the location points on the automotive body components. As such, such previously known framing systems have not been able to maintain precision location of the body components during the assembly process with repeatability after extended operation.
Lastly, these previously known framing systems are very costly to manufacture due in large part to the necessity of the turntable and movable arms.